We request funds to purchase an intravital, multiphoton microscope system (Olympus FV1000MPE) adapted for high resolution intravital imaging in live mice. The new instrument will be housed in the Center for Systems Biology at the Massachusetts General Hospital (MGH) in the new Simches Research building. The system will be part of a larger Bioimaging Platform which brings together several highly successful cores, some of which have been in existence for over 10 years. The mandate of this new core facility is to provide access to a full range of imaging technologies (from microscopic to macroscopic), image analysis, and quantitative methods to individual research groups, funded Centers and the new Thematic Centers within the MGH and the Harvard Medical School (HMS) and MIT community. The reasons for this application are to: 1) provide new in vivo imaging capabilities (including imaging at greater depth) currently not existing within the Core, 2) provide critically needed instrument time to support increasing demand for intravital imaging from current and new users;3) replace an older intravital laser scanning microscope (Olympus IV100) which is on loan from the manufacturer. Since the mouse imaging was founded in 2000, it has become a central part of the MGH/HMS medical research community. Over 70 PHS-funded Principal Investigators within the HMS/MGH and in other institutions have used the facility in the past 3 years. In particular, access to a multiphoton microscope system is now limited by the sheer volume of requests for time and inability to freely transfer animals to other buildings in town for serial imaging and housing outside barrier facilities. For all of the reasons above, a system installed in the Simches Research building is absolutely essential for the Core to continue to provide its services to its existing user base, and at the same time expand its operations to incorporate new users with existing grants.